Fast-response infrared photodetector based on PbS quantum dots for integrated photonic devices characterization

Integrating functionalized quantum dot (QD) components on integrated photonic circuits is an enabling technology to realize unprecedented optical functionalities beyond the capacities of passive photonic devices. Here, we demonstrate a fast-response infrared lead sulfide (PbS) QD photodetector operating at 1550 nm wavelength. Fabricated by a low-cost layer-by-layer process on a 2 cm × 2 cm glass substrate, this device is compatible with wafer-scale large-volume manufacturing. We systematically characterize the absorption properties of the QD solution, QD film, and the final fabricated photodetectors. Our photodetector exhibits a responsivity of 2.61 × 10^-3 A/W at zero bias, which is further boosted to 0.16 A/W at -1 V bias, with photoresponse spanning the telecom S- and C-bands. The photodetector features a -3 dB bandwidth of 4 kHz and a rapid rise time of 86.7 µs. For the first time, we showcase the photodetector in acetylene gas absorption spectroscopy and high-Q tantalum pentoxide microresonator transmission spectrum characterizations, and achieve excellent agreement with the results measured by commercial detectors. This work presents a critical step towards fully integrated QD-incorporated optoelectronic circuits, paving the way to complicated integrated photonic systems that could be deployed for on-chip sensing, optical communication, and optical computing.